Sound reproduction



. O v Patented Man-30,1926. I 71,578,645

U I TE 1S TA TES FF! C e EDWARD B. CRAFT, or HACKENSACK, NEW JERSEY, ASSIGNORYTO WESTERN ELEC- 'rmzo COMPANY, noonrona'rnn, or NEW YORK, N.-Y., A CORPORATION on NEW YORK.

SOUND nnrnonuorron. g y *Appl'i'cationfiled August 1, 192a. Serial N5. 655,638. I To all whom it may concern: speaking telephone apparatus may be em- 55 Be it known that I, 'EDWARD B. CRAFT, a ployed. I, citizen of the United States of America, Referring now to' the drawings, the record residing at. Hackensack, in the county of 1 is rotated in the usual mannerbeneath 15' Bergen and State of New Jersey, have inthe reproducer needle'2, which ismounted vented certain new and useful Improve on the'end of the arm 3 so as to be capable to merits in Sound Reproductions, of which of freely swinging across the record the the followingis; a full, clear, concise, and requisite extent. Arm. 3 is pivotally mount exact description. i 1 ed at 4and at '5 so as "to permitjof move- The present invention relates to the rement of'th'e 'needle'bothin the plane ofthe production of sound from'soun'd records. record and perpendicular to the. record. 05 Among. the objects ofthe invention are?- These parts are shown in plan in Fig. 1, e To secure high quality in sound reproducand the sound undulations in the recordare tion; v I v assumed to he lateralhsolthat the needle To provide for any desired volume of vibrates back andforth in the .,horiZontal reproduced high-quality=sound;m i direction. The needle and its clamping To distribute the reproduced sound as member are mounted .tooscillate with remay lie-desired. spect to the arm 3 about a vertical axis 6. The above and other'objects'of the-inven- Springs 7 may be provided to constrain the 20 tion and the means-for realizing them in needle toward a normal orjequilibriumposipractice will be made clear in the following tion' substantiallyas shown, p I i description iii/connection with the accom- Suitably securedto the needle mounting panying drawings. v and adapted topartake of the needle move- In the, drawings, ments is a small mirror 8 for reflecting a 25 Fig. 1 is a schematic diagram, partly' in beam'of'light froms'ource9 to the photo plan view,'of a sound reproducing system electric cell 10 or other electro'-'responsive according to the invention.

Fig. 2 is adetail view. I 1 14 and cell 10 are mounted on the arm,3

Fig. 3 shows a modified form of reproso that theyswing with it. IThe cell 10 is 30 ducer. Y enclosed in a box 11 which hasfa slit 12 in Briefly and specifically described, the inthe side toward the mirror. This slitisjarvention comprises translating the sound ranged in conjunction witli'the rest of the undulations in a record into variations in optical system so that deflections of the light 'light,translating the light variations into beam produce variationsin theamountor electrical variations, and reproducing sound intensity of illumination of thecell 10. For from the electrical variations after they example, as shown in Fig, 2, the light beam, have been amplified to any desired-extent indicated by the shading, may overlap the I and distributed to any desired -point or slit 12 any desired 'extentywhentheneedle points- I i is in its central or equilibrium position} De- The light variations may be produced by flection of the needle in either direction will light-sensitive device. The light 9, telescope deflecting a beam of light by a mirroractuthen vary the illuminationof the cell. i

ated by the usual reproducer needle when The electrical effects produced between the needle passesover the'sound record or the electrodes of the cell lQare impressed on vice versa. Since the mirror and its 'actuthe amphfier A dla' ram'matically, indicated ating meehanism may be made to have exin' Fig. It will I e understood that any tremely small mass the light variations may desired number of stages of amplification 1 represent to a high degree of accuracy, the maybe employed in addition to the single recordedundulations. The light variations amplifying tube shown,so as to give any produce with vhigh accuracy equivalent elecdesired volume to the: reproduced sound.

5 trical variations, and these, 1n turn, may The amplified current variations maybe readily be amplified with negligible'diston used to actuatera loud-speaking telephone tion to the desiredvolumeand distributed receiving instrument; 13, or'any numberof as desired, ,At the point or points where such instruments, connected either in par the sound 1s to be produced, the usual loudallel or 111 series with each other in any usual or desirable manner. The instrument 13 or amplifier A or both may be positioned at a distance from the cell 10, and in case more than one loud speaker 13 is used, these may be distributed in any desired locations.

The optical system and sound record will, of course, be suitably enclosed in a lighttightchamber.

In operation, the light producing system is adjusted to give a properly shaped beam and the cell 10 is properly positioned by the aid of the adjusting screw 15. These adjustments are preferably such that when the needle 2 occupies the position which it has when traversing a groove free of undulations, the light beam will overlap slit 12 to a considerable extent. As the record rotates, the needle traverses the spiral groove maintaining the beam in this position except as it is deflected by undulations in the :record' groove. The deflections vary the illumination of the cell 10, setting up electrical variations which faithfully follow the recorded sound variations, and when amplified and conveyed to receiver 13, reproduce sound of a desired volume and of high quality;

It will be noted that a very material amplification is obtained by the use of the light beam in the above-described manner, since a very small movement in the mirror 8- produces a large displacement in the beam incident on the photo-electric cell. This also makes for high quality of reproduction since the amplitude through which the mirror oscillates can be extremely small, in fact it can be made smaller than that of the needlepoint itself. a

In Fig. 3, the-mirror 8 is shown mounted on the end of a relatively long arm 16 for the purpose of making the deflections in the reflected beam appear principally as translatory rather than rotary movements. In certain types of optical systems or with special cells -1(), and particularly where thecell is close to the mirror, this type of mounting may be preferable.

It will be obvious from the foregoing description to adapt the invention to records having hill and dale undulations by merely pivoting the mirror 8 by a horizontal Y axis and correspondingly modifying the light system, including slit 12.

The invention is applicable to other types of records than disk records. and is capable of various alterations and modifications from the specific construction shown, the scope of the invention being defined in the claims. I

What is claimed. is:

1. In a sound reproducer, a record having a record groove containing undulations representing sound, an oscillation member mounted so as to be free to oscillate about an axis, means to produce relative movement between said record and said member to bring successive portions of the sound record into operative relation with said member, and to cause oscillations of said member in accordance with the recorded sound undulations, a light-sensitive, electroresponsive element, means to throw a beam of light from said oscillation member to said element, and to vary the illumination of said element by said beam in accordance with the actuation of the member by the sound undulations, means to make the variations in illumination .of said element independent of the position of said axis with respect to said record, and means to produce sound from the resultant electrical effects in said element.

2. In a sound reproducer, a record having a record groove containing undulations representing sound, an arm adapted to swing over said record, a reflector carried on said arm and mounted so as to be free to oscillate with respect to said arm about an axis, a source oflight, a light-sensitive, electroresponsive element, said reflector being positioned so as to illuminate said element with reflected light from said source, means to produce relative movement between said rec- 0rd and said reflector to bring successive portions of said sound record into operative relation with said reflector, and to cause oscillations of said reflector about said axis in accordance with said undulations, the illumination of said element by the reflected light thereby varying in accordance with said sound undulations on said record, said axis of oscillation, said source and said element being positioned With respect to each other so that the variations in the illumination of said element are independent of the position of said arm over said record, and means to produce sound from the electrical variations in said element resulting from the variation in illumination.

3. In combination, a record having a record groove containing undulations representing sound, a reflector, an arm carrying said reflector and adapted to swing over the surface of said record, said reflector be ing mounted so as to be free to oscillate with respect to said arm about an axis perpendicular thereto, a source of light and a lightsensitive electro-responsive element mounted on said arm so as to swing therewith, said reflector being positioned so as to reflect light from said source to said element, means to produce relative movement between said record and said reflector to bring successive portions of the record into'operative relation'with said reflector, and to actuate said reflector in accordance withv the recorded sound undulations, the illumination of said element by reflected light from said source thereby varying in accordance with the sound undulations on said record, means to amplify the resultant electrical variations in said element, and means to produce sound from the amplified electrical variations.

4. In combination, a disc record having undulations representing sound recorded on the surface thereof, a stylus adapted for engagement with said undulations, an arm carrying said stylus and adapted to swing in an are over the surface of said record, said stylus being mounted on the free end of said arm so as to oscillate with respect to said arm about an axis thereon, said arm being pivotally mounted so as to permit movement of said stylus both in the plane of the surface of said record and at an angle thereto, a reflector secured to said stylus and partaking of its movements, a source of light rays and a light sensitive, electro-responsive element mounted on said arm so as to swing therewith, said reflector being positioned so as to reflect a beam of light from said source to said element, means to rotate said record so as to bring successive portions of said recorded undulations into operative relation with said stylus to cause oscillations of said reflector 1n accordance with said undulations, thereby varying in accordance With the sound undulations on the record,

EDWARD B. CRAFT. 

